Are you sure that the CD is finalised as an Audio CD?
To be recognised by iTunes, the CD needs to be finalised, but with most software you have to tell it to finalise. This is so that you can add a few songs to a CD, then add more until it's full. Once finalised, you cannot add any more to an Audio CD, even if there is space on the disc.
But that's not all.
If the CD has MP3 files on it (or most of the other audio formats), then it's not an audio CD. Instead, it's a data disc, with audio files on it. To add those songs to your iTunes Library, use Window Explorer to copy them from the CD to your computer and then use iTunes' menu option File/Add Folder to Library to add them to the library. Navigate to the folder and add that folder. There is also an option to File/Add File to Library for one-off tracks.
Special note about .wav files (or .cda files) on a data disc:
- In the distant past, if one used Window File Manager to examine an Audio CD, each song would appear as a .wav file.
- With Windows 10, Windows Explorer shows the tracks on an Audio CD as .cda files (which I think was how Apple's computers used to show them)
- However, if you examine a data disc that has .wav files on it, you may think it's an Audio CD. It isn't. It's only an Audio CD if the disc was burned as an Audio CD and it has been finalised
Is the disc actually a data disc and not an Audio CD?